qa/tests: run full librbd test suite unconditionally

qa/tests: run full librbd test suite unconditionally

Previously the librbd test runner listed individual gtest filters to
work around unstable groups (see tracker #58791). Those workarounds
are no longer needed, so the script has been simplified to invoke
`ceph_test_librbd` directly. This ensures the entire suite is always
executed and reduces maintenance overhead.

Fixes: https://tracker.ceph.com/issues/58791
Co-authored-by: Matan Breizman <mbreizma@redhat.com>
Signed-off-by: Kautilya Tripathi <kautilya.tripathi@ibm.com>